Caring for aging eyes

In 800 B.C. Homer wrote, "Now the night comes and it is wise to obey
the night." In his time there were frequent muggings at night and home
robberies. Not much has changed since then.

But today we're even more vulnerable, by being involved in tragic car
accidents as the sun goes down. Our eyesight may be to blame. So what happens
to our sight as we age, and how can we decrease the risk of death on the
highway?

A report from The Harvard Medical School states that, "Roadway crashes are
the leading cause of on-the-job fatalities among older workers in the United
States and that poor vision is partly to blame."

Macular degeneration is one of the causes of these accidents. And for those
over the age of 55 years, it's also the main reason for being classified as
"legally blind."

The macula is a pin-sized area in the retina at the back of the eye that
transmits images to the brain.

Like a rifle bullet, it can zero in on small-sized distant objects. And
when the macula develops degenerative changes, nighttime driving becomes
hazardous.

Several other changes occur in the eye as we age. Like other parts of the
body, the eyelids begin to droop, providing less peripheral vision.

The pigmented iris that makes us brown- or blue-eyed isn't present just to
make us pretty.

It also begins to sag as tiny muscles that control the size of the pupil
weaken with age, making it more difficult to keep the iris open.

During our early years the size of the iris is about five millimetres. But
it shrinks to about three millimetres later in life. A smaller pupil allows
less light to strike the retina, making nighttime vision less sharp.

DROOPY EYELIDS

This loss of vision is not detectable during the day. But driving a car
with droopy eyelids and a narrowed pupil has the same effect as wearing
sunglasses while driving at night.

Older drivers are also unable to adapt as quickly to changes in intensity
of light. On occasion we've all complained, "Why didn't that idiot turn off
his high beam?" In this situation, an aging iris contracts more slowly to the
blazing light. But once the car has passed, it's also slow in dilating to
provide more light for the dark road ahead. And a light pigment called
rhodopsin that helps adjust to night vision, decreases as we age.

Today, most people are aware of the risk of developing cataracts in the
lens in later years.

A less transparent lens decreases the amount of light striking the retina
and worsens night driving.

DECREASE HAZARDS

The final problem for the aging eye involves photoreceptors in the retina.
Photoreceptors transmit the image of an upcoming car to the brain. Older
adults can lose one-third of them.

So what can we do to decrease the hazards of driving at night? Mothers
urged us to eat our carrots to maintain good vision and they were partly
right. Carrots are rich in vitamin A needed to regenerate rhodopsin.

There's no sure way to prevent macular degeneration. Some authorities
advise patients to take a daily pill containing lutein, a macular pigment.
They believe that this antioxidant helps to slow down the disease. Others say
eating a diet rich in fruits and vegetables makes more sense.

The only way to improve night vision is cataract surgery.

But there are several studies going back many years that rarely get much
attention. They report that people who take vitamin C show decreased risk of
developing cataracts.

This continues to make sense as, unlike animals, humans do not manufacture
this powerful antioxidant vitamin.

A sure way to survive night driving is to be realistic about your ability
to see well in the dark. And good sense dictates that as visual acuity
decreases, it's prudent to stay away from the steering wheel after sunset.
Homer was right, obeying the night saves lives.

Many readers ask if they can purchase "Extend Plus" in Canada, the
multivitamin/ multimineral combination I recently mentioned in this column. It
can only be obtained by calling the toll-free number 1-800-877-2447.